Астрофизический семинар САО РАН
28 сентября 2017, 13:30, малый зал
Optical supernova remnants in nearby galaxies and their influence on star
formation rates derived from H-alpha emission
In this seminar the influence of Hα emission from supernova remnants (SNRs) on Hα derived star formation rates (SFRs) will be we discussed. The most up-to- date list of nearby galaxies with optically detected SNRs found in literature will be presented. Also, the detection of 16 optical SNR candidates in a part of nearby spiral galaxy IC342, and two more potential SNRs in NGC 185 galaxy will be shown. The candidates were detected by applying [SII]/Hα ratio criterion on narrowband images obtained with the 2m telescope at Rozhen National Astronomical Observatory in Bulgaria. When deriving Hα SFRs, emission from SNRs contaminates Hα flux used to derive SFR. We found that the contribution of SNRs' flux to the total Hα flux, for 18 galaxies in our sample of galaxies with optical SNRs is 5%. Due to the observational selection effects, the SNR contamination of SFRs derived herein represents only a lower limit. M83 is the galaxy with the most detected optical SNRs and in this galaxy SNRs account for 9 per cent of the total Hα emission. We expect that fraction similar to this would be close to the real contribution of SNR emission to the total Hα emission in spiral galaxies.
PROGRESS REPORT ON THE SAO OPTICAL MONITORING OF TYPE 1 AGN
Active galactic nuclei (AGN) are one of the most luminous objects in the Universe, emitting powerful continuum and line emission across all wavelength bands. The resolving of the AGN inner structure is still a difficult task with current instruments, therefore the spectroscopy and spectropolarimetry are crucial tools to investigate these objects and their components, such as the properties of the supermassive black hole and the broad line region (BLR). Moreover, the optical broad emission lines show very complex line profiles and are usually strongly variable in time, which can be use to study the geometry and physics of the BLR, as well as the mass of the supermassive black hole.
Here we give a progress report on the latest result of the long-term optical monitoring of type 1 AGNs. A campaign, which is coordinated by the Special Astrophysical Observatory (SAO) is performed using telescopes of SAO, INAOE and OAN-SPM (Mexico), and Calar Alto (Spain) with the main aim to use the broad line variability to constrain the physics and kinematics of the line emitting regions. In total a dozen of type 1 AGN are observed for decades, and here we outline the latest results.